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Post by dariush on Oct 28, 2022 4:06:58 GMT -5
Hi, we have a problem with a 331 TC that is connected to a closed cycle cryostat. We set the temperature to a value but when that is reached, the heater jumps to "HTR open" and the temperature rushes through to the minimum temperature of the system.
We have set the PID values to 50/20/0 but this does not help.
Any idea what to try next? The connections have been checked several times and are well connected.
Best, Dariush
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Post by dariush on Oct 28, 2022 8:06:40 GMT -5
Addition: I have now opened the TC to check if there was any obvious connection loose inside - but nothing, it all looked good. I have not checked with an amperemeter, though.
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Post by Lake Shore Jeff M on Oct 28, 2022 8:37:37 GMT -5
In the Model 331, the heater protection circuit looks at the heater resistance and if it determines that the heater resistance it sees is greater than 350 ohms, it considers it to be an open circuit.
What resistance do you measure across the prongs of the dual banana plug that connects to the 331. Make the resistance measurement looking toward the heater with the plug disconnected from the 331.
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